The present invention relates to a transport module such as one for use in a high speed mass mail processing and inserting system. The transport provides a staging area for transferring asynchronously produced accumulations of documents generated by the inserter input subsystem to the synchronous transport of the inserter chassis. The transport further provides xe2x80x9cparking spotsxe2x80x9d for accumulations of documents that are already in progress of being created when downstream modules stop.
Inserter systems, such as those applicable for use with the present invention, are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee. Also, other organizations, such as direct mailers, use inserts for producing a large volume of generic mailings where the contents of each mail item are substantially identical for each addressee. Examples of such inserter systems are the 8 series, 9 series, and APS(trademark) inserter systems available from Pitney Bowes Inc. of Stamford, Conn.
In many respects, the typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (other sheets, enclosures, and envelopes) enter the inserter system as inputs. Then, a plurality of different modules or workstations in the inserter system work cooperatively to process the sheets until a finished mail piece is produced. The exact configuration of each inserter system depends upon the needs of each particular customer or installation.
Typically, inserter systems prepare mail pieces by gathering collations of documents on a conveyor. The collations are then transported on the conveyor to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing. Such further processing may include automated closing and sealing the envelope flap, weighing the envelope, applying postage to the envelope, and finally sorting and stacking the envelopes.
The input stages of a typical inserter system are depicted in FIG. 1. At the input end of the inserter system, rolls or stacks of continuous printed documents, called a xe2x80x9cweb,xe2x80x9d are fed into the inserter system by a web feeder 10. The continuous web must be separated into individual document pages. This separation is typically carried out by a web cutter 20 that cuts the continuous web into individual document pages. Downstream of the web cutter 20, a right angle turn 30 may be used to reorient the documents, and/or to meet the inserter user""s floor space requirements.
The separated documents must subsequently be grouped into collations corresponding to the multi-page documents to be included in individual mail pieces. This gathering of related document pages occurs in the accumulator module 40 where individual pages are stacked on top of one another.
The control system for the inserter senses markings on the individual pages to determine what pages are to be collated together in the accumulator module 40. In a typical inserter application, mail pieces may include varying number of pages to be accumulated. For example, the phone bill for a person who lives by himself may be much shorter than the another phone bill representing calls made by a large family. It is this variation in the number of pages to be accumulated that makes the output of the accumulator 40 asynchronous, that is, not necessarily occurring at regular time intervals.
Downstream of the accumulator 40, a folder 50 typically folds the accumulation of documents, so that they will fit in the desired envelopes. To allow the same inserter system to be used with different sized mailings, the folder 50 can typically be adjusted to make different sized folds on different sized paper. As a result, an inserter system must be capable of handling different lengths of accumulated and folded documents.
Downstream of the folder 50, a buffer transport 60 transports and stores accumulated and folded documents in series in preparation for transferring the documents to the synchronous inserter chassis 70. By lining up a back-log of documents in the buffer 60, the asynchronous nature of the upstream accumulator 40 will have less impact on the synchronous inserter chassis 70. For example, if a particularly long phone bill were being formed in the accumulator 40, a larger than normal gap might form with the preceding document. However, this gap will not have an affect on synchronous placement of documents on the chassis 70 because the buffer 60 preferably includes enough documents that the longer document can xe2x80x9ccatch upxe2x80x9d before its turn to be placed on the synchronous chassis 70.
Another important function of the buffer 60 is its ability to xe2x80x9cparkxe2x80x9d document accumulations when the chassis 70 is stopped, or otherwise unable to accept documents. When the chassis 70 must be stopped, for example as a result of a jam, a signal is typically sent to the web feeder 10 and web cutter 20 to cease operating. However, pages that are already in the process of being cut, or that are in the right angle turn 30, or in the folder 50, need a place to come to rest. Such components in the inserter input stage run all the time, and do not have the capability of halting part-way through their processes.
The accumulator 40 typically provides one or two parking spots, or stopping stations, for such documents that are xe2x80x9cin progress.xe2x80x9d However, documents in the accumulator 40 may have to be sent downstream to make room for further xe2x80x9cin progressxe2x80x9d documents from upstream. When the chassis 70 is stopped, there must be at least enough stopping stations in the buffer 60 and accumulator 40 to accept all of the xe2x80x9cin progressxe2x80x9d documents and pages. In particular, when the mail pieces are comprised of shorter numbers of pages, more stopping stations may be needed because more document accumulations result from the same number of pages being cut.
Accordingly, it is desirable that the buffer 60 be designed to include enough stopping stations to satisfy the parameters of the accumulation lengths and page counts as required by the inserter user.
In the prior art buffer depicted in FIG. 2, six stopping stations are provided over a forty-two inch buffer length. The space within each stopping station being seven inches. Each of the prior art stopping stations, 1, 2, 3, 4, 5, and 6, includes a roller nip 14. When a document accumulation must stop at a stopping station, the respective roller nip 14 is stopped. When it is time for a document accumulation to move to the next stopping station, the respective roller nip 14 drives the accumulation downstream.
The seven inch spacing between roller nips 14 is longer than the typical document accumulation to be transported. Accordingly, a mechanism for moving accumulations between roller nips 14 is provided. This mechanism is comprised of o-ring belts 13 that are driven around the length of the buffer transport system by rollers 12. These o-ring belts 13 and rollers 12 run continuously and provide for transportation of accumulations between roller nips 14 at different stopping stations. The o-ring belts 13 continue to run even when one or more of the stopping stations and respective roller nips 14 are stopped. When an accumulation is stopped at the roller nips 14, the o-ring belts 13 slip over and under the accumulations. Accordingly, the tension of the o-ring belts 13 is light, and the surfaces in contact with the accumulations have low friction. As such, rollers 12 and belts 13 are incapable of implementing any control over the stopping and starting of movement of documents in the buffer. Rather, control of the relative movement of documents within the buffer is provided by the roller nips 14.
The roller nips 14 are controlled in accordance with predetermined rules for moving documents within the buffer. When a sensor 11 detects an accumulation within a first stopping station, a decision must be made about what to do with it. Accordingly, when a downstream accumulation is detected in the immediate downstream stopping station, then the accumulation is held in the first stopping station. If there is no accumulation in the immediate downstream stopping station, then the roller nip 14 moves the accumulation downstream to the next station. This logic is used for each of the stopping stations 1-6 for every period in the control cycle. Accordingly, documents are generally shifted towards the downstream end of the buffer as stations become available.
While the prior art system described above often performs satisfactorily, the forty two inch buffer length and seven inch stopping station length are often longer than necessary to handle documents being processed. While these dimensions might be necessary to handle the longest documents to be handled by the inserter system, a more typical letter sized page folded into thirds would be roughly four inches long. Many accumulations are shorter still.
Accordingly, the prior art often uses more floor space than necessary for a given mail piece creation job, and maximum efficiency in storing and transporting documents is not achieved. Floor space being an important consideration for large pieces of equipment such as inserters, it is desirable to achieve the same (or greater) functionality in less space.
The present invention provides a solution to these shortcomings by providing a transport system that can use the available length of the buffer transport to more efficiently meet the particular needs of a given mail piece job run.
Accordingly, the present invention provides a method for controlling the serial transport of articles to achieve and maintain a predetermined gap between transported articles. First and second articles are transported serially on a transport system. The velocities and positions of the first and second articles are measured during the transporting process. The invention operates on a periodic operating cycle. During each period of the operating cycle, an adjustment to the second article is determined based on the various factors including the position of the preceding first article. For each period in the cycle, the invention calculates a current gap between the first and second articles as a function of a distance between a trail edge of the first article and the lead edge of the second article. Then the predetermined gap is subtracted from the current gap to determine a distance the first document is from reaching the edge of the predetermined gap. The controls for the present invention further calculate a minimum displacement needed to decelerate the second article to the velocity of the first article.
This minimum displacement must be considered it is desirable that the predetermined gap be maintained even if the first article comes to a halt at its maximum deceleration. If the second trailing article is traveling faster than the first article, even if decelerating at the same rate as the first article, more displacement will be required before coming to a complete stop. Accordingly, an additional spacing must be maintained to take into account a stopping displacement differential resulting from the second article traveling faster than the first article.
Based on these calculations the control system determines if the distance from the second document to the edge of the gap is substantially the same as the minimum deceleration distance. If so, then the second article is accelerated (or decelerated) at a calculated acceleration to ensure that the minimum deceleration distance does not encroach into the predetermined gap, and that the second document continues to approach the predetermined gap. The calculated acceleration is a function of a maximum acceleration parameter of the transporting means, the starting velocity of the second article, and the velocity of the first article. The calculated acceleration may be positive or negative depending on the whether the second article is going faster or slower than the first article.
Further details of the present invention are provided in the accompanying drawings, detailed description and claims.